The present invention relates to a control apparatus for an internal combustion engine, the engine having a variable valve duration mechanism that changes the valve duration of an intake valve, and performs cooperative control for the intake valve duration and the opening degree of a throttle valve, thereby adjusting the intake air amount.
Conventionally, to accelerate the warm-up after starting an engine, several measures have been taken. Such measures include setting a high idling speed and retarding the ignition timing for increasing the amount of heat used for the warm-up.
Also, a system including a variable valve duration mechanism has been applied to internal combustion engines. In such a system, the variable valve duration mechanism changes the valve duration of the intake valves (see Japanese Laid-Open Patent Publication No. 2001-263015). In an internal combustion engine having the system, the amount of air drawn into the combustion chambers can be decreased by reducing the valve duration of the intake valves. In this case, for example, pumping loss is reduced by a greater degree by reducing the opening degree of the throttle valve than by reducing the intake air amount. That is, loss of the power of the internal combustion engine is reduced. Accordingly, the fuel economy is improved.